1. Field of the Invention
The present invention relates to electromagnetic interference (EMI) shielding and more particularly, to a door assembly for an EMI shielded room.
2. Background of the Invention
Shielded rooms are used to prevent egress and ingress of electromagnetic radiation. The radiation in question may be ambient radiation generated from outside activities or radiation generated inside the room and which must be confined therein.
The shielded room typically comprises walls, ceiling, and floors covered with one or more layers of electrically conductive metal sheets, meshing, or screening. An electrically conductive door is often provided so that personnel may enter and leave the room. When the door is closed, the gap between the door leaf and the jamb must be shielded from electromagnetic radiation encroachment and the shield on the door leaf must be continuously and intimately connected to the room shielding along the entire periphery of the door where the door opposes the jamb.
One approach has been to use resilient contact fingers along the edges of the door (see U.S. Pat. No. 4,786,758). A disadvantage in this design is the force exerted on the resilient fingers when the door is opened or closed, said force often leading to breakage or deformation of the fingers.
Other invented devices feature bladders mounted on the door leaf which facilitate the outward extension of the shield substrate from the interior of the door (see U.S. Pat. Nos. 5,786,547 and 5,569,878). While elegant in design, these bladder configurations result in a bulky and expensive door leaf having a substantial number of moving parts.
Generally, inclusion of moving parts, bladders, tubing and other intricate items within the confines of a door tend to make the door less tolerant to shock and heat.
A need exists in the art for an EMI enclosure door leaf having no moving parts except for its handle and transport mechanisms such as the hinges or hangers. The door should be capable of attenuating electromagnetic radiation up to 100 dB. Also the door should be capable of withstanding temperatures of up to 927° C. (1700° F.) for approximately 90 minutes.